Image sensor, image-sensing apparatus using the image sensor, and image-sensing system

ABSTRACT

An image sensor has a plurality of pixels, each pixel including a photoelectric converter and a pixel circuit for processing signals from the photoelectric converter and outputting processed signals and a scanning circuit, disposed between the photoelectric converters, included in each of at least two adjacent pixels among a plurality of pixels aligned in a single direction. An edge pixel accommodates, in order from an edge of the image sensor toward an interior, a predetermined empty region, a photoelectric converter and a pixel circuit. There is at least one position at which two adjacent pixels, the first of the two pixels accommodating, in order, a pixel circuit, a photoelectric converter and predetermined empty region, the second accommodating, in order, a predetermined empty region, a photoelectric converter and a pixel circuit. The scanning circuit is disposed in the predetermined empty region between the two adjacent pixels.

RELATED APPLICATIONS

This application is a continuation of application Ser. No. 11/100,889,filed Apr. 6, 2005, which is a continuation of application Ser. No.10/231,243, filed Aug. 29, 2002, now U.S. Pat. No. 6,906,332. Thisapplication claims benefit of both applications under 35 U.S.C. § 120,claims benefit under 35 U.S.C. § 119 of Japanese patent application no.2001/261740, filed Aug. 30, 2001, and incorporates by reference theentire disclosure of each of the three mentioned prior applications.

FIELD OF THE INVENTION

The present invention relates to an image sensor for sensing an image,an image-sensing apparatus using the image sensor, and an image-sensingsystem using the image-sensing apparatus.

BACKGROUND OF THE INVENTION

Advances in digital technology have found increasingly wide applicationin the field of medicine in general and radiology in particular. Atwo-dimensional radiographic apparatus for radiological use has beendeveloped in order to digitalize X-ray images, in which a scintillatoris used to convert the X-rays into visible light that is then sensed andformed into a diagnostic image by image sensors.

As two-dimensional radiographic apparatuses, compact CCD image sensorsfor use in dentistry have already been commercialized, and formammography and thoracic X-ray use a large-scale, still-image sensingapparatus using maximum 43 cm-square panels of amorphous silicon hasbeen produced. Image sensors that use amorphous silicon semiconductorsformed on a glass substrate can be formed easily into large panels, andlarge-scale radiographic apparatuses have been achieved using four tilesof such panels. An example of this type of technology is described inU.S. Pat. No. 5,315,101.

Similarly, a large-panel radiographic apparatus comprising a pluralityof monocrystalline image sensors (such as silicon image sensors) hasbeen proposed. An example of this type of technology is U.S. Pat. No.5,159,455, shown in FIG. 12. Silicon-based CCD-type image sensors andMOS- or CMOS-type image sensors may be used for the monocrystallineimage sensors.

Further advances in the digitalization of medical radiographicdiagnostics are expected, in the form of still more sensitivestill-image sensing apparatuses and next-generation, moving-imagesensing apparatuses.

In this case, acquiring a moving image necessitates directing acontinuous X-ray onto a human subject. The known adverse effects onliving tissue of prolonged exposure to X-ray radiation, however, make itdesirable to reduce the intensity of X-ray to, e.g., 1/100 of normalintensity and to employ read speeds of 60-90 frames/sec, which in turnrequires apparatuses that are several tens of times faster and moresensitive than ordinary still-image acquisition equipment.

The process of manufacturing an amorphous silicon panel image-sensingapparatus possesses the advantage of yielding larger panels compared tothe process for manufacturing CCD image sensors and CMOS image sensors,but with the disadvantage that it is more difficult to carry out fineprocessing of a semiconductor on a glass substrate than on amonocrystalline silicon semiconductor substrate, and as a result theoutput signal line capacitance increases. This capacitance is thelargest source of noise (kTC noise) and limits improvements insensitivity. Moreover, with amorphous silicon the semiconductorcharacteristics are not enough to increase the speed of operation, sothat acquisition of moving images at speeds of 30 frames/sec or more isdifficult.

CCD image sensors, though of the complete-depletion type and thereforesensitive, are unsuited as wide-area image-sensing elements. A CCD imagesensor is a charge transfer device, so as the area (i.e., the number ofpixels) increases and the number of transfer steps grows large, transferbecomes a problem. In other words, the drive voltage is different at thedrive terminal and near the center, making complete transfer difficult.In addition, power consumption, which may be expressed as CVf² (where Cis the capacitance across the substrate and the well, V is the pulseamplitude, and f is the pulse frequency) experiences a ten-fold increasecompared to that of a CMOS image sensor because C and V increase as thearea increases. As a result, the drive circuitry in this area generatesheat and noise, degrading the S/N ratio. For these reasons a CCD-typeimage sensor is not suitable as a large-scale image sensor.

In a simple large-panel image-sensing apparatus using a multiplicity ofmonocrystalline image sensors, dead space is inevitably created whereverthe image sensors adjoin (necessitated by the need for a region separatefrom the pixel region for providing peripheral circuitry such as a shiftregister, multiplexer and amplifier, external terminals for transmittingsignals and power to and from an external device and a protectivecircuit composed of a protective diode or a protective resistanceagainst static electricity). This dead-space portion leads to linedefects (that is, gaps in the image) and a deterioration in picturequality. For this reason a tapered FOP (fiber optic plate) is used todirect light from a scintillator around the dead spaces and toward theimage sensor pixel region. However, such a configuration requires a veryexpensive tapered FOP, which increases production costs. Moreover, atapered FOP has a disadvantage in that the sharper the angle of taperthe harder it is for light from the scintillator to enter the taperedFOP, which leads to a decrease in output light level that can offset thesensitivity of the image sensors and reduce the overall sensitivity ofthe apparatus.

SUMMARY OF THE INVENTION

Accordingly, the present invention has been made in consideration of theabove-described situation, and has as its object to preventdeterioration in picture quality due to line gaps in the picture imagearising from dead space at the edges where adjacent panels meet in aconfiguration in which a plurality of image sensor panels are joinedtogether to create a large image sensor, and to prevent deterioration inpicture quality due to slight deviations in pitch between respectivephoto-receptor portions.

According to the present invention, the above-described object isattained by an image sensor having a plurality of pixels, each pixelincluding a photoelectric converter and a pixel circuit for processingsignals from the photoelectric converter and outputting processedsignals to an output line, and a scanning circuit, disposed between thephotoelectric converters, included in each of at least two adjacentpixels among a plurality of pixels aligned in a single direction. Anedge pixel of the plurality of pixels accommodates, in order from anedge of the image sensor toward an interior of the image sensor, apredetermined empty region, a photoelectric converter and a pixelcircuit. The plurality of pixels have at least one position at which twopixels are disposed adjacent to each other, a first of the two pixelsaccommodating, in order, a pixel circuit, a photoelectric converter andpredetermined empty region, a second of the two pixels accommodating, inorder, a predetermined empty region, a photoelectric converter and apixel circuit. The scanning circuit is disposed in the predeterminedempty region between the two adjacent pixels.

In addition, according to the present invention, the above-describedobject is also attained by an image-sensing apparatus comprising aplurality of the image sensors described above.

In addition, according to the present invention, the above-describedobject is also attained by an image-sensing system that includes theimage-sensing apparatus described above, a signal processing circuitadapted to process signals from the image-sensing apparatus, a recordingcircuit adapted to record the signal processed by the signal processingcircuit, and a display circuit for displaying the signal processed bythe signal processing circuit.

In addition, according to the present invention, the above-describedobject is also attained by an image sensor having a plurality of pixels,each pixel including a photoelectric converter and a pixel circuit forprocessing signals from the photoelectric converter and outputtingprocessed signals to an output line, and a processing circuit adapted toprocess signals from the plurality of pixels, disposed between thephotoelectric converters, included in each of at least two adjacentpixels among a plurality of pixels aligned in a single direction. Anedge pixel of the plurality of pixels accommodates, in order from anedge of the image sensor toward an interior of the image sensor, apredetermined empty region, a photoelectric converter and a pixelcircuit. The plurality of pixels have at least one position at which twopixels are disposed adjacent to each other, a first of the two pixelsaccommodating, in order, a pixel circuit, a photoelectric converter anda predetermined empty region, a second of the two pixels accommodating,in order, a predetermined empty region, a photoelectric converter and apixel circuit. The processing circuit is disposed in the predeterminedempty region between the two pixels disposed adjacent to each other.

In addition, according to the present invention, the above-describedobject is also attained by an image-sensing apparatus having a pluralityof the image sensors described above.

In addition, according to the present invention, the above-describedobject is also attained by an image-sensing system that includes theimage-sensing apparatus described above, a signal processing circuitadapted to process signals from the image-sensing apparatus, a recordingcircuit adapted to record the signal processed by the signal processingcircuit, and a display circuit for displaying the signal processed bythe signal processing circuit.

Other features and advantages of the present invention will be apparentfrom the following description, taken in conjunction with theaccompanying drawings, in which like reference characters designate thesame or similar parts throughout the figures thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of the specification, illustrate embodiments of the invention and,together with the description, serve to explain the principles of theinvention.

FIG. 1 is a diagram showing the arrangement of the parts that comprisethe pixels of the image sensor of the image-sensing apparatus accordingto a first embodiment of the present invention;

FIG. 2 is a diagram showing an expanded view of part A of FIG. 1;

FIG. 3 is a diagram showing the arrangement of the parts that comprisethe pixels not arranged symmetrically every two pixels;

FIG. 4 is a diagram showing an equivalent circuit in a case in which twopixels are in a mirror-image arrangement;

FIG. 5 is a schematic diagram showing a circuit structure of a circuitpart having a 4×5 pixel arrangement;

FIG. 6 is a diagram showing an arrangement of a photoelectric converter,a pixel circuit part and a vertical shift register in a single pixelaccording to a first embodiment of the present invention;

FIG. 7 is a diagram showing a plan view of a wafer and an image sensorcreated therefrom according to a first embodiment of the presentinvention;

FIG. 8 is a diagram showing a plan view of an array of image sensors andan array of scanning circuits in an image-sensing apparatus according toa first embodiment of the present invention;

FIG. 9 is a cross-sectional view of the image-sensing apparatusaccording to a first embodiment of present invention, along a line A-A′shown in FIG. 8;

FIG. 10 is a block diagram of a radiographic apparatus according to asecond embodiment of the present invention;

FIG. 11 is a schematic diagram of a radiographic apparatus adapted to aradiographic diagnostic system according to a third embodiment of thepresent invention;

FIG. 12 is a diagram showing an example of a conventional image-sensingapparatus; and

FIG. 13 shows a variation of the image-sensing apparatus according to afirst embodiment, in which a pixel arrangement is varied horizontally inorder to accommodate a scanning circuit.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments of the present invention will be described indetail in accordance with the accompanying drawings.

First Embodiment

FIG. 1 is a plan view of a CMOS-type image sensor according to a firstembodiment of the present invention.

In the first embodiment, as will be described later, nine image sensortiles are arranged to form a large-panel image-sensing apparatus. In adiagnostic radiographic apparatus, the size of the pixels can berelatively large, that is, squares of approximately 100 μm to 200 μm aside. In the present first embodiment, the size of the pixel isapproximately 160 μm a side.

FIG. 2 is a diagram showing an expanded view of part A of FIG. 1. InFIG. 2, the relation between adjacent image sensors is also shown.

In both FIG. 1 and FIG. 2, reference numeral 1 denotes the boundary linebetween pixels, reference numeral 2 denotes a photoelectric converter(that is, a photodiode), reference numeral 3 denotes a pixel circuit(including pixel-internal amplifier, pixel selection switch, resetswitch and transfer switch). The photoelectric converter 2 and the pixelcircuit 3 together form a single pixel, with the pixels arrangedhorizontally and vertically in columns and rows, that is, in twodimensions.

Reference numeral 4 denotes a vertical scan control block, which is alogic circuit, that includes a vertical shift register as a verticalscanning circuit that controls all pixels in a single horizontal lineand also performs reset, pixel selection and charge transfer in order toscan vertically. Reference numeral 5 denotes a horizontal scan controlblock that includes a shift register as a horizontal scanning circuitfor sequentially outputting signals from a horizontal line of pixels andalso includes a shared processing circuit such as a serial-parallelconversion multiplexer, a buffer, gates and output amplifiers forprocessing output signals from a horizontal line of pixels.

Reference numeral 6 denotes a terminal for connecting to an externalcircuit, reference numeral 7 denotes a bump for providing an electricalconnection between the terminal 6 and a flexible tape (not shown in thediagram), and reference numerals 8 and 9 denote a protective resistanceand a protective diode, respectively, for protecting the circuits insidethe image sensor from static electricity from external sources.

In addition, in FIG. 2, reference numeral 10 denotes a slice marginregion and reference numeral 11 denotes a composite margin region (gap).

In an image-sensing apparatus that combines a plurality of imagesensors, in order to obtain a full image without line gaps it isnecessary to arrange the centers of gravity of the photoelectricconverters 2 within and between the image sensors at the same pitch (inthe present first embodiment, at the above-described distance of 160μm). It is more preferable if the photoelectric converters 2 have thesame area within and between image sensors. With such an arrangement, afull image of uniform sensitivity with no change in pitch between linegaps can still be obtained even with slice margins 10 at the edges ofthe image sensors and even with composite margins (gaps) 11 betweenimage sensors. In such a case, there is no need for image processingsuch as the line gap interpolation that is required in order to correctfor the dead space (defective or non-existent pixel region) arising atthe gaps between a plurality of image sensors as in the conventionalimage-sensing apparatus.

As shown in FIG. 2, in the present invention according to a firstembodiment, the pixels are arranged at a uniform pitch both within theimage sensors and between image sensors. Moreover, the centers ofgravity of the photoelectric converters of the pixels are also arrangedat the same pitch horizontally and vertically. Moreover, the areas ofthe photoelectric converters inside all the pixels inside the imagesensors are the same. In the present embodiment, this is achieved by thearrangement of the pixel circuits 3 and the photoelectric converters 2inside the pixels, and further by the shift registers provided insidethe pixel regions of the image sensors as described below.

As shown in FIG. 2, the pixels that contact the edges of the imagesensors have an effective area (the region on which photoelectricconverters can be arranged) that is smaller than that of other pixelsdue to the slice margin and the composite margin. When arranging thephotoelectric converters 2 and the pixel circuits 3 inside these pixelsso that the photoelectric converters 2 are arranged at the same pitchand the same area within image sensors as well as between image sensors,the pixel circuits 3 are arranged symmetrically about a hypotheticalline drawn between pixels arranged along an edge of the image sensor andadjacent pixels inside the image sensor, in other words so-calledmirror-image arrangement. In the present embodiment, the elements thatcomprise the pixel circuits 3 (that is, a pixel-internal amplifier,pixel selection switch, reset switch and transfer switch) are alsoarranged symmetrically.

The photoelectric converters 2 are also arranged symmetrically about aline parting the pixel circuits 3. Further, the pixel circuits 3 of thetwo rows of pixels adjacent to these two rows (or two lines) are alsoarranged symmetrically about a hypothetical line contacting the pixels.

Moreover, with such an arrangement, an empty space is formed betweenevery two rows of photoelectric converters. The photoelectric converters2 are also arranged symmetrically about this empty space. In thisembodiment, a vertical shift register that is a vertical scan circuit isdisposed in this single row of empty space where no pixel circuit 3 isprovided. Further, a horizontal shift register that is a horizontal scancircuit, a multiplexer, a buffer, a shared amplifier and the like areprovided as appropriate in the other empty spaces.

In the preceding paragraph, a name “horizontal” shift register is usedfor convenience in view of its electrical function that transfers andoutputs charges of each row in the order of the pixels in the row.However, the “horizontal” shift register is arranged along a “vertical”empty space.

Next, a description is given of the advantages of the above-describedmirror-image arrangement as compared to a case in which such anarrangement is not used, by comparing FIG. 2 with FIG. 3.

FIG. 3 is a diagram showing the arrangement of the parts that comprisethe pixels not arranged symmetrically every two pixels. Basically,photoelectric converters having the same area as those shown in FIG. 2are disposed apart at a pitch of 160 μm. However, in order to make thedistance between centers of photoelectric converters 2 within andbetween image sensors uniform, the photoelectric converters 2 and thepixel circuits 3 in the pixels at the edges, which have a smaller pixelarea than other pixels due to the slice margin and composite margin,must also be disposed at the same pitch.

In such a case, as shown in FIG. 3, in order to dispose these elementsat the same pitch the area of the photoelectric converters 2′ at theedge pixels becomes very small and so the edge pixel sensitivity alsodeclines substantially. In the worst case, the photoelectric converterscannot function as photo detectors at all and become essentiallydefective pixels, making it difficult to obtain a full image withoutline gaps. Moreover, since the area for providing a scanning circuit isso reduced (in this case the space width is so narrow), even if it werepossible to mount a shift register with a simplified structure it wouldnevertheless be difficult to fit a logic circuit or a scanning circuitsuch as a decoder or a shift register having a complex logic forperforming complex scanning of an image adder inside the pixel region.The area (in this case the width) of the photoelectric converters 2 ofthe pixels around the scanning circuit can be reduced and a region forthe scanning circuit can be secured, but to the extent possible, it ispreferable to make the pitch and the area of the photoelectricconverters 2 identical in order to obtain a full image with no linegaps. Space for the scanning circuits can also be secured by reducingthe area of the photoelectric converters 2 of all the pixels andsecuring the same pitch and area, but such an approach leads inevitablyto a loss of overall sensitivity and is not preferable in terms ofobtaining a sensitive image-sensing apparatus.

Here, by employing the structure of the first embodiment as shown inFIG. 2, the area of the photoelectric converters can be maximized andphotoelectric converters themselves can be arranged at the same pitch,and moreover, a wide region for accommodating the scanning circuits canbe secured within the pixel regions.

Similarly, by giving the pixel circuits 3 a mirror-image circuitarrangement, the power lines needed for every row of pixels in theconventional art can now be laid at every other row of pixels, therebyreducing the opportunity for manufacturing defects in the power lines(opens and shorts) to arise. As will be described later, where a singlelarge-panel image sensor obtained from a single wafer is employed, thewiring for the image sensor can approach some 136 mm in length if laidend to end, and it is manufacturing defects in this wiring that has agreat impact on the picture quality of the image sensor. Themirror-image arrangement of the present embodiment can improve theyield, and the resulting production cost reductions can be significantin the case of such large-panel image sensors as are described herein.

In the present invention according to the first embodiment, the verticalshift register, a horizontal shift register, a multiplexer, outputamplifier, external terminal, and static electric protection. circuits(protection resistance and protection diode) connected to the externalterminal which are conventionally disposed around the outer periphery ofthe conventional image sensor are disposed in the image sensor pixelregion. Such an arrangement turns the entire surface of the image sensorinto a pixel region, so when such an image sensor is compiled intotiles, there is no dead space along its periphery (that is, along thefour sides of the image sensor). When a 3×3 span of tiles are alignedside-to-side there is essentially no gap between them, so such a circuitstructure can form a seamless, large-panel image-sensing apparatus.

As described above, in a diagnostic radiographic apparatus, the size ofthe pixels can be as large as 50 μm to 200 μm a side (as describedabove, the present embodiment uses 160 μm a side), so sufficientaperture can be achieved even with the mounting of shift registers inthe pixel region.

In the present embodiment, the shift registers are disposed within thepixel region, so X-rays passing through the scintillator hit the shiftregisters directly. Lead-containing FOP is used as an X-ray shieldingmember, but even so it is difficult to provide complete protection. Theshift registers circuits are used to sequentially transmit pulsesignals, so static shift registers are used as the shift registers.

Static-type shift registers are relatively unaffected by X-rays, so theycan be used where they may be exposed directly by X-rays as in thepresent embodiment. Accordingly, by using static-type shift registers,an image-sensing apparatus little affected by X-ray-induced damage orerror, that is, with improved reliability, can be achieved.

In addition, the present embodiment also uses CMOS-type image sensorsfor the image sensors, which consume little power and are well-suited toform large-panel image-sensing apparatuses.

Moreover, the inclusion of the multiplexer inside the image sensorspeeds up the operation of the image sensor.

Moreover, signals are fed externally from the image sensors via theterminal 6, but because stray capacitance around the terminal 6 islarge, an amplifier is provided in the stage previous to the terminal 6so the signal transmission characteristics can be corrected.

FIG. 4 is a diagram showing an equivalent circuit in a case in which twopixels are in a mirror-image arrangement. In the first embodiment asdescribed above, the elements that make up the pixel circuits 3 (thepixel-internal amplifiers, the pixel selection switches, the restswitches, the transmit switches) are also arranged symmetrically, so theequivalent circuit, too, expresses the same arrangement.

In FIG. 4, PD denotes a photodiode that performs photoelectricconversion and accumulates the electrical charge generated by thatphotoelectric conversion, C_(FD) denotes the floating diffusioncapacitor that stores an electrical charge, M1 denotes a transmissionMOS transistor (transmission switch) that transmits the electricalcharge generated by the photodiode to the floating diffusion CFD, M2denotes a reset MOS transistor (reset switch) that discharges theelectrical charge stored in the C_(FD), M3 denotes a selection MOStransistor that selects the pixel, M4 denotes an amplifier MOStransistor (pixel amplifier) that functions as a source follower, andreference numeral 40 denotes a signal output line.

FIG. 5 is a schematic diagram showing a circuit structure having a 4×5pixel arrangement. A φTX(n) signal from the vertical block 4 that is atype of vertical scanning circuit is applied to the gate of thetransmission switch M1, a φRES(n) signal from the vertical block 4 isapplied to the gate of the reset switch M2, and a φSEL(n) signal fromthe vertical block 4 is applied to the gate of the selection switch M3.It should be noted that (n) denotes the line that applies the signals.In order to simplify the drawing, only the aforementioned three controllines are drawn. The noise signals and the photoelectric convertedsignals from the pixels are output through the signal wire 40 to adifferential amplifier (not shown in the drawing) via a horizontal block5 (including a horizontal shift register, a multiplexer, and so on).

FIG. 6 is a diagram showing an arrangement of a unit block (unit forselecting and driving one line) of the vertical shift register of thevertical block 4 together with a photodiode of a photoelectric converter2 and a pixel circuit 3 and in a unit area (single pixel) according to afirst embodiment of the present invention. It should be noted that theequivalent circuit diagram for the single pixel (the photoelectricconverter 2 and the pixel circuit 3) is depicted in FIG. 4.

For simplicity of explanation, the surface area of the photodiode PD(photoelectric converter 2) and of the pixel circuit 3 are not shown atactual size but have been schematized.

Here, a simple circuit, composed of the static-type shift registers andthe transmission gates, for producing the transmission signal φTX, thereset signal φRES and the selection signal φSEL is shown as the verticalshift register. This simple circuit is driven by a clock signal from aclock signal line (not shown in the diagram). The circuit structure ofthe shift registers is not limited to this embodiment but may be anydesired circuit structure depending on how it is driven, (addition orintervallic read-out, for example).

By disposing the shift register functional blocks between the pixels asshown in the first embodiment described above, the shift registers canbe provided within the effective pixels region, turning the entiresurface of an image sensor into pixel region.

As can be appreciated by those of ordinary skill in the art, ann-to-2^(n) decoder may be used instead of the shift registers as ascanning circuit. By connecting to the decoder input the output of acounter that sequentially increments, it becomes possible tosequentially scan like the shift registers. By inputting the address ofthe region one wishes to acquire an image of to the decoder input, animage can be obtained of any desired region by random scanning.

FIG. 7 is a diagram showing a plan view of a wafer and an image sensorcreated therefrom according to a first embodiment of the presentinvention. The wafer shown is the current mainstream 8-inch size. Usinga CMOS process, a single 136 mm-square CMOS image sensor is produced.

FIG. 8 is a diagram showing a plan view of an array of image sensors andan array of scanning circuits in an image-sensing apparatus according toa first embodiment of the present invention. More specifically, FIG. 8shows the image sensor portion of a large-area radiographic apparatuscreated by combining nine 136 mm-square tiles of image sensors havingpixel structures into a 408 mm-square large-area radiographic apparatusshown here, in which the image sensor tiles are combined so that pitchesat the borders between the tiles are equal to the pitch within eachtile. (For ease of depiction, the FOP and the scintillator are not shownin the diagram.)

FIG. 9 is a cross-sectional view of the image-sensing apparatusaccording to a first embodiment of present invention, along a line A-A′shown in FIG. 8. A scintillator 91 composed of Gd₂O₂S and CsI usingeuropium and terbium as inert elements is disposed atop a FOP 92.Although in the present embodiment a leaded FOP is used as anon-magnification optical transmission system, a non-magnification lensarray, such as a two-dimensional selfoc lens array, used in combinationwith leaded glass may be used instead. The light utilization rate of anon-magnification lens array is not as good as that of an FOP, but it isinexpensive and its use can lower the production cost of theimage-sensing apparatus overall. Alternatively, the image sensorsthemselves can be given an X-ray-resistant device structure, thuseliminating the need to use a non-magnification optical transmissionsystem that shields X-rays and allowing the scintillator 91 to bedisposed directly on the image sensor. In this case, the scintillator 91and the image sensors are joined together using an optically transparentadhesive agent, which may be resin. If the transparent adhesive agent isthin enough, it can be interpreted as the non-magnification opticaltransmission system. The X-rays are then incident on the scintillator 91and are converted into visible light. The visible light is then sensedby the image sensors. It is preferable to select the scintillator 91whose emission light wavelengths are suitable for the sensitivity of theimage sensors. An external processing board 93 supplies power and aclock to the image sensors, and additionally, has a circuit thatacquires and processes signals from the image sensors. The flexible tapeprovides an electrical connection between the image sensors and theexternal processing board 93. TAB (Tape—Automated Bonding) may be usedas the flexible tape.

The nine tiles of image sensors are essentially glued together withoutgaps between the image sensors. Here, the term “essentially withoutgaps” means that the image formed by the nine image sensors has nomissing pixels. The image sensor clock, the power input and the outputof the signals from the image sensors are fed through the flexible tapeconnected to the terminal 6 provided on the edge portion of the imagesensor and to the external processing board 93 provided on the rear ofthe image sensors. The thickness of the flexible tape is from 20 μm to30 μm and sufficiently thin for the widths involved so that no defectsappear in the image even when passing through gaps between the imagesensors.

As described above, according to the first embodiment, by repeatedlyarranging in a predetermined direction two pixels composed of one pixelarranged in the sequence of a predetermined empty region, aphotoelectric converter and a pixel circuit and another pixel arrangedin the sequence of pixel circuit, photoelectric converter andpredetermined empty region, and by providing a scanning circuit such asa vertical block 4 or a horizontal block 5 in a desired empty region soas to form a large-panel image sensor from a combination of a pluralityof smaller image sensor panels, deterioration in picture quality at thejunction of the image sensor panels as well as deterioration in picturequality due to unevenness in the pitch between respective photoreceptorscan be prevented.

In addition, as can be appreciated by those of ordinary skill in theart, the first embodiment is not limited to an instance in which twopixels having the structure described above are repeated horizontally.Rather, the first embodiment also includes an instance in which, of theplurality of pixels arranged horizontally, the leftmost pixelaccommodates, in rotating repetitive order, a predetermined emptyregion, a photoelectric converter, and a pixel circuit, and therightmost pixel accommodates, in rotating repetitive order, a pixelcircuit, a photoelectric converter, and a predetermined empty region(the order of arrangement in both cases being from left to right), andfurther, a pixel accommodating a pixel circuit, a photoelectricconverter, and a predetermined empty region (in that order) and a pixelaccommodating a predetermined empty region, a photoelectric converterand a pixel circuit, in that order, are positioned adjacent to eachother in order for a scanning circuit to be provided at at least onelocation, such that the remaining pixels may be of any arbitrarycompositional sequence or order. An example of such a situation isillustrated in FIG. 13.

FIG. 13 shows a variation of the image-sensing apparatus according to afirst embodiment, in which a pixel arrangement is varied horizontally inorder to accommodate a scanning circuit. In FIG. 13, reference numeral 1denotes an image sensor edge part, reference numeral 2 denotes aphotoelectric converter, reference numeral 3 denotes the pixel circuit 3and reference numeral 4 denotes the vertical scanning circuit.

The above arrangement can also prevent deterioration in picture qualityat the junction of the image sensor panels as well as deterioration inpicture quality due to unevenness in the pitch between respectivephotoreceptors, when a large-panel image sensor is formed from acombination of a plurality of smaller image sensor panels.

Second Embodiment

A description is now given of a second embodiment of the presentinvention, with reference to the accompanying drawings.

FIG. 10 is a block diagram of a radiographic apparatus according to asecond embodiment of the present invention.

As shown in the diagram, an image of a subject 103 (in this case, aperson's chest) is acquired by irradiation from an X-ray source 102. Theimage sensing unit 101 is composed of the image-sensing apparatus of thefirst embodiment, a scintillator that converts radiation to visiblelight, an X-ray shielding member and peripheral drive circuitry.

A 4×8 signal (that is, a signal output from a 9×2 output line from nineimage sensors) from an image sensor unit 101 is converted from analog todigital by a signal A/D converter 105 and an FPN A/D converter 106. Animage sensor drive unit 104 is mounted adjacent to the image sensor unit101.

The nine frames of A/D converted image signals undergo combiningoperation and defective noise correction by an image processing circuit107 and a memory 109. The processed signal is then either recorded to arecording unit 111 or displayed at a display unit 110 (that is, amonitor), and printed as necessary. The aforementioned circuitry andapparatuses are controlled entirely by a controller 108. The controller108 also controls the triggering of the X-ray source 102 and the imagesensors.

Signals temporarily stored in the memory 109 then undergo imageprocessing (.gamma.-processing and interpolation, etc.) so as to composea single image from the signals from the image sensors. The processedoutput is then stored to a large-scale image memory, and the memoryoutput is displayed at a display unit 109 such as a monitor. When imageacquisition is complete the process terminates. The data taken into theimage-sensing apparatus is transmitted to a personal computer or thelike, where the data is further processed, typically using a softwareapplication program, for diagnosis of the subject image.

The image processing described above can be performed using a programstored in a personal computer or the like. Similarly, the presentinvention includes a CD ROM or other such storage medium on which suchprogram is recorded. By reading out the program recorded on such a CDROM, the image processing method according to the above-described secondembodiment of the present invention can be executed.

Third Embodiment

A description is now given of a third embodiment of the presentinvention, with reference to the accompanying drawings.

FIG. 11 is a schematic diagram of a radiographic apparatus adapted to aradiographic diagnostic system according to a third embodiment of thepresent invention.

As shown in the diagram, X-rays 6060 produced by an X-ray tube 6050 passthrough the chest area 6062 of a patient or test subject 6061 and into aradiographic apparatus 6040 comprising a scintillator, an FOP, imagesensors, as those shown in FIG. 9, and an external processing board (notshown). The scintillator generates light in response to the influx ofthe X-ray radiation 6060 and the image sensors convert the light toelectrical signals to obtain electrical information. The information isthen digitalized and processed by an image processor 6070 for viewing ona first display 6080 in a control room.

In addition, the information described above can be transmitted to aremote location by a transmission means. The transmission means may bean ordinary telephone line 6090. The remote location may be aphysician's office, and the information so transmitted can be displayedon a second display 6081 in the office or stored on a storage medium.The storage medium may be an optical disk. Such an arrangement enables aphysician at a remote location to view the radiographic image andprovide a diagnosis. Similarly, the information can be recorded on film6110 by a film processor.

As can be appreciated by those of ordinary skill in the art, the presentinvention is not limited to the above-described embodiments, and variouschanges and modifications can be made within the spirit and scope of thepresent invention. Therefore, in order to apprise the public of thescope of the present invention, the following claims are made.

1. An image sensor comprising: a plurality of pixels, each pixelincluding a photoelectric converter and a pixel circuit for processingsignals from the photoelectric converter and outputting processedsignals to an output line, the plurality of pixels having at least oneposition at which a first pixel, a second pixel, a third pixel, andfourth pixel are arranged in a one direction, in order, wherein thepixel circuit of the first pixel and the pixel circuit of the secondpixel are arranged between the photoelectric converter of the firstpixel and the photoelectric converter of the second pixel, and the pixelcircuit of the third pixel and the pixel circuit of the fourth pixel arearranged between the photoelectric converter of the third pixel and thephotoelectric converter of the fourth pixel, and the first pixel, thesecond pixel, the third pixel, and the fourth pixel are arranged so thatthe photoelectric converters are arranged at the same pitch; and ascanning circuit disposed between the photoelectric converter of thesecond pixel and the photoelectric converter of the third pixel.
 2. Theimage sensor according to claim 1, wherein the photoelectric converterof the first pixel, the photoelectric converter of the second pixel, thephotoelectric converter of the third pixel, and the photoelectricconverter of the fourth pixel have the same area.
 3. The image sensoraccording to claim 1, wherein the pixel circuit of each pixel comprisesan amplifier unit adapted to amplify a signal from the photoelectricconverter, and a reset unit adapted to reset an input part of theamplifier unit.
 4. The image sensor according to claim 1, furthercomprising an empty space disposed between the photoelectric converterof the second pixel and the photoelectric converter of the third pixel,wherein the scanning circuit is disposed in the empty space.
 5. An imagesensor comprising: a plurality of pixels, each pixel including aphotoelectric converter and a pixel circuit for processing signals fromthe photoelectric converter and outputting processed signals to anoutput line, the plurality of pixels having at least one position atwhich a first pixel, a second pixel, a third pixel, and fourth pixel arearranged in a one direction, in order, wherein the pixel circuit of thefirst pixel and the pixel circuit of the second pixel are arrangedbetween the photoelectric converter of the first pixel and thephotoelectric converter of the second pixel, and the pixel circuit ofthe third pixel and the pixel circuit of the fourth pixel are arrangedbetween the photoelectric converter of the third pixel and thephotoelectric converter of the fourth pixel, and the first pixel, thesecond pixel, the third pixel, and the fourth pixel are arranged so thatthe photoelectric converters are arranged at the same pitch; and aprocessing circuit, adapted to process signals from the plurality of thepixels, disposed between the photoelectric converter of the second pixeland the photoelectric converter of the third pixel.
 6. The image sensoraccording to claim 5, wherein the photoelectric converter of the firstpixel, the photoelectric converter of the second pixel, thephotoelectric converter of the third pixel, and the photoelectricconverter of the fourth pixel have the same area.
 7. The image sensoraccording to claim 5, wherein the pixel circuit of each pixel comprisesan amplifier unit adapted to amplify a signal from the photoelectricconverter, and a reset unit adapted to reset an input part of theamplifier unit.
 8. The image sensor according to claim 5, furthercomprising an empty space disposed between the photoelectric converterof the second pixel and the photoelectric converter of the third pixel,wherein the scanning circuit is disposed in the empty space.
 9. An imagesensor, comprising: a plurality of pixels, each pixel including aphotoelectric converter and a pixel circuit for processing signals fromthe photoelectric converter and outputting processed signals to anoutput line, the plurality of pixels having at least one position atwhich a first pixel, a second pixel, a third pixel, and fourth pixel arearranged in a one direction, in order, wherein the pixel circuit of thefirst pixel and the pixel circuit of the second pixel are arrangedbetween the photoelectric converter of the first pixel and thephotoelectric converter of the second pixel, and the pixel circuit ofthe third pixel and the pixel circuit of the fourth pixel are arrangedbetween the photoelectric converter of the third pixel and thephotoelectric converter of the fourth pixel, and the first pixel, thesecond pixel, the third pixel, and the fourth pixel are arranged so thatthe photoelectric converters are arranged at the same pitch; and a logiccircuit disposed between the photoelectric converter of the second pixeland the photoelectric converter of the third pixel.
 10. The image sensoraccording to claim 9, wherein the photoelectric converter of the firstpixel, the photoelectric converter of the second pixel, thephotoelectric converter of the third pixel, and the photoelectricconverter of the fourth pixel have the same area.
 11. The image sensoraccording to claim 9, wherein the pixel circuit of each pixel comprisesan amplifier unit adapted to amplify a signal from the photoelectricconverter, and a rest unit adapted to reset an input part of theamplifier unit.
 12. The image sensor according to claim 9, furthercomprising an empty space disposed between the photoelectric converterof the second pixel and the photoelectric converter of the third pixel,wherein the scanning circuit is disposed in the empty space.